html_doc = """
<html><head><title>The Dormouse's story</title></head>
    <body>
        <p class="title" ><b>The Dormouse's story</b></p>
        <p class="story">0nce upon a time there were three little sisters; and their nanes were
        <a href= "http://example.com/elsie" class=" sister" id="link1">Elsie</a>,
        <a href= "http://example.com/lacie" class="sister" id=" link2">Lacie</a> and
        <a href= "http://example.com/tillie" class="sister" id=" link3">Tillie</a>;
        and they lived at the bottom of a well. 
    </p>

<p class-" story">...</p>
"""
from bs4 import BeautifulSoup
soup=BeautifulSoup(html_doc,'lxml')

fand=soup.find_all('a')
for data in fand:
    """方法一"""
    # href=data.get('href')
    # print(href)
    """方法二"""
    print(data['href'])